This invention relates to an information transferring method and apparatus for transferring information stored in a memory area to another memory area, and particularly to a method and apparatus for rotating information of a memory area and transferring a rotated information to another memory area.
The above method and apparatus is used, for example, in an image processing field. When information displayed on a location of a screen is moved to another location, information stored in a video memory must be transferred from a source area, in which information to be transferred is stored, to a destination area by using a memory to memory transferring method. In a case information of a plurality of bits is transferred, a long period of time must be spent if the information is transferred bit by bit therefore, a block transfer by which a plurality of bits can be transferred altogether is effective. To perform the block transfer, the video memory is accessed word by word by word addresses.
However, when a boundary of the source area or the destination area does not coincide with a boundary of an accessed word, heretofore a shifting operation for shifting a bit location in the word has been used to adjust the word to the source area or the destination area. This shifting operation is required for each word, so that a high-speed block transfer cannot be performed. Further, since a lower bit or bits of a shifted word stick out an adjacent word, a writing operation for the destination area is difficult as described hereinafter. Particularly, when information in the source area is rotated, a bit-boundary in a word is varied by a rotator, so that the above shifting operation becomes more complex.